1. Field of the Invention
The present invention relates to a honeycomb structure and a method for manufacturing the honeycomb structure.
2. Discussion of Background
Many technologies have been developed for converting exhaust gases from automobiles. However, due to an increase in traffic, it is hard to say that countermeasures for controlling exhaust gases have been satisfactorily taken. Meanwhile, restrictions on exhaust gases from automobiles will be further strengthened domestically and worldwide.
In order to harmonize with such restrictions, catalyst carriers capable of processing predetermined components contained in exhaust gas have been used in exhaust gas systems. Further, as members of such catalyst carriers, honeycomb structures have been used.
Such honeycomb structures have plural cells (through-holes) extending from one end face to the other end face along its longitudinal direction, and the cells are separated from one another by cell walls on which a catalyst is carried. Therefore, when exhaust gas is caused to pass through such honeycomb structures, the catalyst carried on the cell walls converts (oxidizes and reduces) substances such as HC (hydrocarbon compounds), CO (carbon monooxide), and NOx (nitrogen oxide) contained in the exhaust gas. Consequently, such components in the exhaust gas can be processed.
Generally, the cell walls (substrates) of such honeycomb structures are made of cordierite. Further, the cell walls have a catalyst carrying layer made of γ-alumina, and a precious metal catalyst such as platinum and/or rhodium is carried on the catalyst carrying layer.
Further, in order to enhance conversion performance at an exhaust gas temperature lower than a temperature at which a catalyst becomes active, there has been proposed a technology for providing a honeycomb structure having relatively low resistance with electrodes for applying voltage and energizing the same so as to cause the honeycomb structure to heat by itself (JP-U-49-124412).
The contents of JP-U-49-124412 are incorporated by reference herein.